DE 199 00 264 A1 describes, using a tie rod for a motor vehicle as an example, a structural unit comprising a tube which is provided on at least one side with an internal thread which turns in a first direction of rotation, wherein a threaded sleeve having a corresponding external thread is screwed into the end of the tube. A shank of a ball joint is screwed into this threaded sleeve. For this purpose, the shank has an external thread which turns in the direction opposite to the first direction of rotation and corresponds to the internal thread of the threaded sleeve. By moving the threaded sleeve, which has a key surface extending out of the open end of the tube for attaching a tool for this purpose, the tube and the shank can be moved relative to each other in the axial direction. This means that rotating the threaded sleeve causes the tube and the shank to move towards each other or away from each other. This condition is brought about by the threads which progress in opposing directions. This adjustment mechanism can be used to adjust the length of the structural unit, which is significant with regard to adjusting the track of the vehicle, in particular in the case of the example of a tie rod for motor vehicles presented in the document. In the case of the solution according to DE 199 00 264 A1, it is disadvantageous, however, that the threaded sleeve extends out of the open end of the tube. In this section at least, when used in motor vehicles in particular, there is a risk that corrosion can occur on the free end of the threaded sleeve due to damage or improper handling when adjusting the length of the structural unit. The fundamental risk therefore also exists that this corrosion will expand to the adjacent components, thereby causing the structural unit to become untight or, possibly, permanently unusable.
Document DE 77 32 250 U1 describes a structural unit that is designed similarly to the previously described tie rod and likewise enables the threaded sleeve to be adjusted via a key surface provided for this purpose, and therefore the shank and the tube can move relative to each other in the axial direction.
A disadvantage of this solution, however, is that both the tube and the threaded sleeve screwed into it each comprise at least one longitudinal slot which enables moisture or contaminants to enter the interior of the structural unit, in particular when the structural unit is used in a motor vehicle. An increased load on the threaded regions caused by the foreign substances entering them cannot be ruled out entirely, and there is a potential risk of premature wear or premature ageing of the structural unit and, therefore, there is a risk that functionality will be limited, at the least.